High plus treatment zone lens design and method for preventing and/or slowing myopia progression

ABSTRACT

Contact lenses incorporate high plus or add power profiles that at least one of slow, retard or preventing myopia progression and minimize halo effect. The lens includes a center zone with a negative power for myopic vision correction; and at least one treatment zone surrounding the center zone, the at least one treatment zone having a power profile that increases from an outer margin of the center zone to a positive power within the at least one treatment zone of greater than +5.00D.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to ophthalmic lenses, and moreparticularly, to contact lenses designed to slow, retard, or preventmyopia progression. The ophthalmic lenses of the present inventioncomprise a high plus or high add treatment zone, thereby preventingand/or slowing myopia progression.

Discussion of the Related Art

Common conditions which lead to reduced visual acuity are myopia andhyperopia, for which corrective lenses in the form of spectacles, orrigid or soft contact lenses, are prescribed. The conditions aregenerally described as the imbalance between the length of the eye andthe focus of the optical elements of the eye. Myopic eyes focus in frontof the retinal plane and hyperopic eyes focus behind the retinal plane.Myopia typically develops because the axial length of the eye grows tobe longer than the focal length of the optical components of the eye,that is, the eye grows too long. Hyperopia typically develops becausethe axial length of the eye is too short compared with the focal lengthof the optical components of the eye, that is, the eye does not growenough.

Myopia has a high prevalence rate in many regions of the world. Ofgreatest concern with this condition is its possible progression to highmyopia, for example greater than five (5) or six (6) diopters, whichdramatically affects one's ability to function without optical aids.High myopia is also associated with an increased risk of retinaldisease, cataracts, and glaucoma.

Corrective lenses are used to alter the gross focus of the eye to rendera clearer image at the retinal plane, by shifting the focus from infront of the plane to correct myopia, or from behind the plane tocorrect hyperopia, respectively. However, the corrective approach to theconditions does not address the cause of the condition, but is merelyprosthetic or symptomatic.

Most eyes do not have simple myopia or hyperopia, but have myopicastigmatism or hyperopic astigmatism. Astigmatic errors of focus causethe image of a point source of light to form as two mutuallyperpendicular lines at different focal distances. In the foregoingdiscussion, the terms myopia and hyperopia are used to include simplemyopia or myopic astigmatism and hyperopia and hyperopic astigmatismrespectively.

Emmetropia describes the state of clear vision where an object atinfinity is in relatively sharp focus with the crystalline lens relaxed.In normal or emmetropic adult eyes, light from both distant and closeobjects and passing though the central or paraxial region of theaperture or pupil is focused by the crystalline lens inside the eyeclose to the retinal plane where the inverted image is sensed. It isobserved, however, that most normal eyes exhibit positive longitudinalspherical aberration, generally in the region of about +0.50 Diopters(D) for a 5.0 mm aperture, meaning that rays passing through theaperture or pupil at its periphery are focused +0.50 D in front of theretinal plane when the eye is focused to infinity. As used herein themeasure D is the dioptric power, defined as the reciprocal of the focaldistance of a lens or optical system, in meters.

The spherical aberration of the normal eye is not constant. For example,accommodation (the change in optical power of the eye derived primarilythough change to the internal crystalline lens) causes the sphericalaberration to change from positive to negative.

As noted, myopia typically occurs due to excessive axial growth orelongation of the eye. It is now generally accepted, primarily fromanimal research, that axial eye growth can be influenced by the qualityand focus of the retinal image. Experiments performed on a range ofdifferent animal species, utilizing a number of different experimentalparadigms, have illustrated that altering retinal image quality can leadto consistent and predictable changes in eye growth.

Furthermore, defocusing the retinal image in both chick and primateanimal models, through positive lenses (myopic defocus) or negativelenses (hyperopic defocus), is known to lead to predictable (in terms ofboth direction and magnitude) changes in eye growth, consistent with theeyes growing to compensate for the imposed defocus. The changes in eyelength associated with optical blur have been shown to be modulated bychanges in both scleral growth and choroidal thickness. Blur withpositive lenses, which leads to myopic blur and decreases scleral growthrate, results in hyperopic refractive errors. Blur with negative lenses,which leads to hyperopic blur and increases scleral growth rate, resultsin myopic refractive errors. These eye growth changes in response toretinal image defocus have been demonstrated to be largely mediatedthrough local retinal mechanisms, as eye length changes still occur whenthe optic nerve is damaged, and imposing defocus on local retinalregions has been shown to result in altered eye growth localized to thatspecific retinal region.

In humans there is both indirect and direct evidence that supports thenotion that retinal image quality can influence eye growth. A variety ofdifferent ocular conditions, all of which lead to a disruption in formvision, such as ptosis, congenital cataract, corneal opacity, vitreoushemorrhage and other ocular diseases, have been found to be associatedwith abnormal eye growth in young humans, which suggests that relativelylarge alterations in retinal image quality do influence eye growth inhuman subjects. The influence of more subtle retinal image changes oneye growth in humans has also been hypothesized based on optical errorsin the human focusing system during near work that may provide astimulus for eye growth and myopia development in humans.

One of the risk factors for myopia development is near work. Due toaccommodative lag or negative spherical aberration associated withaccommodation during such near work, the eye may experience hyperopicblur, which in turn stimulates myopia progression as discussed above.Moreover, the accommodation system is an active adaptive optical system;it constantly reacts to near-objects, as well as optical designs. Nomatter what optical designs one puts on the eye, when the eyeaccommodates to near-objects, continuous hyperopic defocus will bepresent and make the eye myopic. Therefore, one way to design optics toslow the rate of myopia progression is to utilize a high plus signal tothe retina through use of high add or plus powers.

U.S. Pat. No. 6,045,578 discloses that the addition of positivespherical aberration on the contact lens will reduce or control theprogression of myopia. The method includes changing the sphericalaberration of an ocular system by a direction and degree related toalter the growth in eye length, in other words emmetropization may beregulated by spherical aberration. In this process, the cornea of amyopic eye is fitted with a lens having increasing dioptric power awayfrom the lens center. Paraxial light rays entering the central portionof the lens are focused on the retina of the eye, producing a clearimage of an object. Marginal light rays entering the peripheral portionof the cornea are focused in a plane between the cornea and the retina,and produce positive spherical aberration of the image on the latter.This positive spherical aberration produces a physiological effect onthe eye which tends to inhibit growth of the eye, thus mitigating thetendency for the myopic eye to grow longer.

Although the level of positive spherical aberration and/or plus powerrequired to achieve an optimum slowdown in the myopia progression rateis unclear, researchers in the field have attempted to use multi-zonedevices with regions of positive power of about +1.50 to a maximum of+3.00D add in an attempt to slow the progression of myopia. The approachresulted in treatment results of less than about 50 percent. Treatmentefficacy is defined as the relative change of axial length and/orspherical equivalent refraction from baseline for a test group comparedto the change of axial length and/or spherical equivalent refraction ofa control group over a year or a predetermined time period. Thereremains a need for a myopia control treatment with efficacy greater than50 percent and closer to 100 percent. Intuitively adding treatment zonesof high plus power would provide greater treatment as the ocular growthresponse in animals was proportional to the power of the opticalstimulus as reported by Wildsoet, Vision Research 1995.

However, conventional wisdom in the field of bifocal or multifocalophthalmic lenses assumes lenses with high plus or high add power mayhave deleterious effects on vision and contrast sensitivity as reportedby Ardaya et al, Optometry 2004. Further, Smith et al (U.S. Pat. No.7,025,460) teaches against going to powers outside the range normallyfound in bifocal or multifocal lenses for presbyopia. They state “It isimportant to note that, while the appropriate type of refractive defocuscan drive eye growth (or non-growth) leading to myopia (or itsregression) in the phenomenon of lens compensation, when the amount ofrefractive defocus is great, there may be such a large degradation inimage quality due to the severe defocus that the optical state maychange into the phenomenon of form deprivation and may induce myopia inthat way.” Further, they teach “that the maximum amount of relativecurvature of field before substantial vision degradation occurs, whichleads to form deprivation myopia, to be around the spherical equivalentof +3.50D to +4.00D, which represents the upper limit for negativecurvature of field for effective treatment of myopia.” This belief hasdiscouraged researchers from pursuing high plus treatment zones formyopia control.

To the contrary, applicant's research shows that using a design with acentral distance zone and a high plus or high add treatment zone havinga plus power greater than about 3.00D reduces visual acuity lossrelative to low conventional plus type designs with no significantadditional impact on contrast sensitivity. This is also supported inrecent work by De Gracia et el, OVS 2013, although they onlyinvestigated up to 4.00D of add power and did not relate the work to apotential benefit in myopia progression control. This breakthroughenables ophthalmic designs to achieve a meaningful greater than 50percent slowdown in myopia progression without further negativelyimpacting visual acuity.

Further, significantly higher plus power relative to the distance poweris not expected to lead to reduced accommodation as may occur with alower add power design where a subject might rely to some extent on theadd power for clear vision during near work activities, as has beenobserved during the course of our research. This reduced accommodationmay lead to hyperopic defocus of rays passing through the distanceportion of the device. In the current invention, the subject mustaccommodate over the distance portion of the lens for near visioncorrection as objects imaged through the treatment zones of high pluspowers are sufficiently out of focus that they cannot be cleared withthe accommodation-convergence system.

Another researchers in the field, R. Griffin WO2012/173891, claims torelieve accommodative lag and accommodative stresses that lead to myopiaprogression through the creation of an artificial pinhole that resultsin increased depth of focus and depth of field. In their intellectualproperty, “the eye's accommodation is more relaxed” in contrast to thepresent invention.

With reference now to FIG. 1, the graph illustrates a device with adesign that incorporates a distance zone to correct for distance visionand a peripheral zone of variable plus power. Visual acuity was measuredusing a four forced choice method with progressively smaller Snellenoptotypes. Increasing peripheral plus power to about +2.00D to +3.00Dcauses an increasing loss of high contrast visual acuity, as typical ofmultifocal type designs for presbyopes. As the peripheral powercontinues to increase; however, the relative effect on visual acuitysurprisingly improves and plateaus, so that by above about +4.00D to+5.00D peripheral plus, the visual acuity loss becomes relativelyconstant. This is of significance for the design of myopia controllenses, since higher plus power is found (with animal models) to have agreater impact on eye growth, as reported in Wildsoet, Vision Research1995.

However, further optimization of plus power designs is required tooptimize image quality. With reference now to FIG. 2, power profiles areillustrated having +5.00D or +10.00D power beyond a 2.25 mm radiallocation from a center of a lens. Rays passing through these high plusor high add power regions form sharp foci in front of the retina.However, due to continued propagation to the retina, these rays form aring-like defocus blur on the retina.

As shown in the point spread function (PSF) cross section of FIG. 3,rays coming from the +5.00D and +10.00D regions form separate spikes onthe retina. Thus, if one looks at a point light source through one ofthese +5.00D or +10.00D high plus lenses, his/her retina would receive apeak signal surrounded by a ring-like halo. Usually, this is not aproblem when one reads letters or resolves fine details of objectsbecause the halo is so dim that the human doesn't perceive it.Nevertheless, this is a problem if a person looks at a black/white edge,as energy from the white background can leak into the black due to thepresence of the spike in PSF.

With reference now to FIG. 4, the image cross section for the +5.00D and+10.00D power profiles of FIG. 2 at an entrance pupil size of 6.0 mm areshown by convolving the PSF with the black/white edge in object space. Alens having 0.00D power forms a sharp edge between the black and white(at 0.0 mm location) and thus doesn't have a ring-like structure. On theother hand, the lenses with +5.00D and +10.00D regions do not have asharp edge between black and white, thereby resulting in images in whichthe black background is not completely black, and the white backgroundis not completely white.

Accordingly, the presence of halo is an inherent property of high plusor high add lens designs. The present invention is directed to lenseshaving high plus power treatment zones that are suitable for the use intreating, controlling, or reducing the progression of myopia while alsominimizing a halo effect.

SUMMARY OF THE INVENTION

The lens design of the present invention overcomes the limitations ofthe prior art by providing lenses that ensure distance vision correctionand have high plus power treatment zones that treat, control, or reducethe progression of myopia while also minimizing a halo effect.

In accordance with one aspect, the present invention is directed to anophthalmic lens for at least one of slowing, retarding or preventingmyopia progression and for minimizing a halo effect. An ophthalmic lenscomprises a center zone with a negative power for myopic visioncorrection and at least one treatment zone surrounding the center zone.The at least one treatment zone has a power profile that increases froman outer margin of the center zone to a positive power within the atleast one treatment zone of greater than +5.00D. For optimum distancecorrection, the power profile within the distance power region can beflat based on subject correction requirement or progressively vary toaccount for the cornea positive or negative spherical aberration.

In accordance with another aspect, the present invention is directed toa method for at least one of slowing, retarding or preventing myopiaprogression. An ophthalmic lens is provided comprising a center zonewith a negative power for myopic vision correction and at least onetreatment zone surrounding the center zone, the at least one treatmentzone having a power profile that increases from an outer margin of thecenter zone to a positive power within the at least one treatment zoneof greater than +5.00D. Accordingly, the growth of the eye is altered.For optimum distance correction, the power within the distance powerregion can be flat based on subject correction requirement orprogressively vary to account for the cornea positive or negativespherical aberration.

The contact lens of the present invention is designed with a powerprofile having at least one high plus or high add treatment zone. As setforth herein, the at least one treatment zone minimizes a halo effect ata black/white edge.

The lens design of the present invention may also be customized toachieve both good foveal vision correction and higher treatment efficacybased on the subject's average pupil size.

The high plus contact lens design of the present invention provides asimple, cost-effective and efficacious means and method for preventingand/or slowing myopia progression which is increasing throughout theworld.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIG. 1 illustrates a graph showing changes in visual acuity as pluspower is added in a peripheral zone.

FIG. 2 illustrates power profiles of two lenses, one having a +5.00Dtreatment zone and the other having a +10.00D treatment zone.

FIG. 3 illustrates a cross section of the point spread function for thepower profiles of FIG. 2 at an entrance pupil size of 6.0 mm.

FIG. 4 illustrates an image cross section of the power profiles of FIG.2.

FIG. 5a illustrates a point spread function for five power profiles.

FIG. 5b illustrates the image cross section of the power profiles ofFIG. 5 a.

FIGS. 6a-c illustrates power profiles of three lenses according to thepresent invention.

FIGS. 7a-c illustrates the image cross section of the power profiles ofFIGS. 6a-c , respectively.

FIGS. 8a-c illustrates power profiles of three additional lensesaccording to the present invention.

FIG. 9 is a diagrammatic representation of an exemplary contact lens inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, an ophthalmic lens has atleast one high plus or high add treatment zone surrounding a center zonefor treating, preventing, or slowing myopia progression while alsominimizing any halo effect at a black/white edge.

With reference now to FIG. 5a (inset graph), five power profiles areillustrated: 1) a power profile having a +5.00D treatment zone; 2) apower profile having a +10.00D treatment zone; 3) two zig-zag orsawtooth power profiles with periodic power modulation between about+5.00D and about +12D; and 4) a power profile having a gradual powerincrease from +5.00D to +12.00D.

In the PSF cross section of FIG. 5a (main graph), the two ring spikes ofthe +5.00D and +10.00D add power profiles have a much higher intensitythan the other three power profiles, because the latter three designshave continuous power modulation. On the other hand, the latter threedesigns carry wider ring spikes. The convolution between the spikes withwider width and lower intensity yields a smooth transition of halointensity between black and white edges, as shown in FIG. 5b (insetgraph), as compared to the sharp edges for the +5.00D and +10.00D powerprofiles, as shown in the main graph of FIG. 5b . As a result of thesmooth transition, human vision finds any halo effect for the latterthree power profiles less bothersome than the halo effect resulting fromthe abrupt intensity profiles.

With reference now to FIGS. 6a-6c , the power profiles of three lensdesigns according to the present invention are illustrated. For eachdesign, the power profile comprises a center zone, which may have anegative focal power to correct existing a myopic distance visioncondition (i.e., paraxial power). The diameter of the center zone may beabout 3 mm to about 7 mm, for example 4.3 mm. Each lens design alsocomprises at least one treatment zone that surrounds the center zone.The at least one treatment zone carries a large amount of high add orhigh plus power relative to the power in the center zone.

As illustrated in FIGS. 6a-b , the power profiles rise gradually andcontinuously from a margin of the center zone (point A) to a pointwithin the at least one treatment zone (point B). In specificembodiments, the location of point B is between 3.0 mm and 4.5 mm from acenter of the lens. The at least one treatment zone may remain constantfrom point B to a margin of an optic zone (point C, for example at 4.5mm). As illustrated in FIG. 6c , the power profile may zig-zag oroscillate as the power rises from point A to point B and/or point C anddoes not need to be monotonic. In specific embodiments, the at least onetreatment zone may have a dioptric power ranging from about +1D to about+15D.

According to the present invention, a gradual and/or periodic change ofplus power in the at least one treatment zone mitigates the halo effectbecause such variations smoothen the intensity profile at sharp blackand white edges. The halo intensity profiles of the three lens designsof FIGS. 6a-c are shown in FIGS. 7a-c , respectively. All three designshave a smooth halo intensity profile at the black/white edge.

While lenses of the present invention are designed so that the halobecomes less bothersome to the human eye, it may be difficult to reducethe halo effect when the lens becomes decentered on the eye. When a lensdecenters, the ring-like structure in PSF becomes asymmetric, and energywill shift from one side of PSF to another side. As a result, one sideof ring-like structure in PSF will have a much higher intensity, and thehalo intensity will increase. The halo will become obvious regardless tothe halo intensity profile. Hence, the utilized lens geometrical designshould preferably result in good lens centration on the eye to furtherminimize potential for the visual artifacts.

With reference now to FIGS. 8a-c , the power profiles for threeadditional lens designs according to the present invention areillustrated. These three lens designs have 1) at least one enhancedtreatment zone in which power is added within the center zone, and 2) atleast one treatment zone. The at least one enhanced treatment zone mayvary in diameter from about 0.5 mm to about 1.0 mm. The power magnitudeof the at least one enhanced treatment zone may range from about +1D(FIG. 8a ) to about +10D (FIGS. 8b-c ). The at least one treatment zonehave a gradual and/or period change in plus or add power as discussedabove or may have a stepped increase in plus or add power. The powermagnitude of the at least one treatment zone may range from about +5D toabout +15D (FIGS. 8b-c ).

Referring now to FIG. 9, there is illustrated a schematic diagrammaticview of a contact lens 900 in accordance with an embodiment of thepresent invention. The contact lens 900 comprises an optic zone 902 andan outer zone 904. The optic zone 902 comprises a first, center zone 906and at least one peripheral zone 908. In specific embodiments, thediameter of the optic zone 902 may be selected to be 8.0 mm, thediameter of the substantially circular first zone 906 may be selected tobe 4.0 mm, and the boundary diameters of an annular outer peripheralzone 908 may be 5 mm and 6.5 mm as measured from the geometric center ofthe lens 900. It is important to note that FIG. 9 only illustrates anexemplary embodiment of the present invention. For example, in thisexemplary embodiment, the outer boundary of the at least one peripheralzone 908 does not necessarily coincide with the outer margin of theoptic zone 902, whereas in other exemplary embodiments, they maycoincide. The outer zone 904 surrounds the optic zone 902 and providesstandard contact lens features, including lens positioning andcentration. In accordance with one exemplary embodiment, the outer zone904 may include one or more stabilization mechanisms to reduce lensrotation when on eye.

It is important to note that the various zones in FIG. 9 are illustratedas concentric circles, the zones may comprise any suitable round ornon-round shapes such as an elliptical shape.

It is important to note that as the entrance pupil size of the eyevaries among subpopulations, in certain exemplary embodiments, the lensdesign may be customized to achieve both good foveal vision correctionand myopic treatment efficacy based on the patient's average pupil size.Moreover, as pupil size correlates with refraction and age for pediatricpatients, in certain exemplary embodiments, the lens may be furtheroptimized towards subgroups of the pediatric subpopulation with specificage and/or refraction based upon their pupil sizes. Essentially, thepower profiles may be adjusted or tailored to pupil size to achieve anoptimal balance between foveal vision correction and minimization ofhalo effect resulting from a high plus or high add treatment zone.

Currently available contact lenses remain a cost effective means forvision correction. The thin plastic lenses fit over the cornea of theeye to correct vision defects, including myopia or nearsightedness,hyperopia or farsightedness, astigmatism, i.e. asphericity in thecornea, and presbyopia, i.e., the loss of the ability of the crystallinelens to accommodate. Contact lenses are available in a variety of formsand are made of a variety of materials to provide differentfunctionality.

Daily wear soft contact lenses are typically made from soft polymermaterials combined with water for oxygen permeability. Daily wear softcontact lenses may be daily disposable or extended wear disposable.Daily disposable contact lenses are usually worn for a single day andthen thrown away, while extended wear or frequent replacement disposablecontact lenses are usually worn for a period of up to thirty days.Colored soft contact lenses use different materials to provide differentfunctionality. For example, a visibility tint contact lens uses a lighttint to aid the wearer in locating a dropped contact lens, enhancementtint contact lenses have a translucent tint that is meant to enhanceone's natural eye color, the color tint contact lens comprises a darker,opaque tint meant to change one's eye color, and the light filteringtint contact lens functions to enhance certain colors while mutingothers. Rigid gas permeable hard contact lenses are made fromsiloxane-containing polymers but are more rigid than soft contact lensesand thus hold their shape and are more durable. Bifocal contact lensesare designed specifically for patients with presbyopia and are availablein both soft and rigid varieties. Toric contact lenses are designedspecifically for patients with astigmatism and are also available inboth soft and rigid varieties. Combination lenses combining differentaspects of the above are also available, for example, hybrid contactlenses.

It is important to note that the lens designs of the present inventionmay be incorporated into any number of different contact lenses formedfrom any number of materials. Specifically, the lens design of thepresent invention may be utilized in any of the contact lenses describedherein, including, daily wear soft contact lenses, rigid gas permeablecontact lenses, bifocal contact lenses, toric contact lenses and hybridcontact lenses. In addition, although the invention is described withrespect to contact lenses, it is important to note that the concept ofthe present invention may be utilized in spectacle lenses, intraocularlenses, corneal inlays and onlays.

Although shown and described is what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

1. An ophthalmic lens for at least one of slowing, retarding orpreventing myopia progression in a patient, the ophthalmic lenscomprising: a treatment zone with a negative dioptric power adapted tocorrect myopic vision of said patient; and at least one enhancedtreatment zone having an ADD power relative to said negative dioptricpower of said treatment zone, wherein said ADD power is between +5D and+15D, wherein the at least one enhanced treatment zone is positioned ata center of said ophthalmic lens and extends to a radius of about 0.7 mmfrom said center.
 2. The ophthalmic lens according to claim 1, whereinthe ADD power within said enhanced treatment zone is between +10D and+15D.
 3. The ophthalmic lens according to claim 1, wherein the ADD powerwithin said enhanced treatment zone is a stepped increase in add power.4. The ophthalmic lens according to claim 22, further comprising asecond enhanced treatment zone having an ADD power relative to saidnegative dioptric power of said treatment zone.
 5. The ophthalmic lensaccording to claim 4, wherein said enhanced treatment zone has a radiusof 0.75 mm.
 6. An ophthalmic lens for at least one of slowing, retardingor preventing myopia progression in a patient, the ophthalmic lenscomprising: a first zone having zero dioptric power; and at least oneenhanced treatment zone having an ADD power relative to said zerodioptric power of said first zone, wherein said ADD power is between +5Dand +15D, wherein the at least one enhanced treatment zone is positionedat a center of said ophthalmic lens and extends to a radius of about 0.7mm from said center.
 7. The ophthalmic lens according to claim 6,wherein the ADD power within said enhanced treatment zone is between+10D and +15D.
 8. The ophthalmic lens according to claim 6, wherein theADD power within said enhanced treatment zone is a stepped increase inadd power.
 9. The ophthalmic lens according to claim 6, furthercomprising a second enhanced treatment zone having an ADD power relativeto said zero dioptric power of said treatment zone.
 10. The ophthalmiclens according to claim 9, wherein said enhanced treatment zone has aradius of 0.75 mm.